Oskar Sigvaldason worked with Acres International, a global consulting engineering and management services company, for 38 years, including nine years as President. He is Owner and President of SCMS Inc., which provides consulting, management and governance services, with special focus on infrastructure development and climate change.

He worked on several major projects, including the Churchill Falls Project in Labrador, the Schrumm Project (Bennett Dam) in British Columbia, the Three Gorges Project in China (Advisory Board) and as Project Manager for the Karnali Multi-purpose Water Project in Nepal (which included dedicated hydro export to India). His career also included managing preparation of national investment and strategic development plans, with funding from international agencies, for energy and electricity supply for Indonesia, Bangladesh, Kenya, Tanzania, Ethiopia, Sudan and Ghana. He also managed river basin development programs including planning, operations and system dispatch, for river systems in Canada, United States, China, Nepal, Sri Lanka, South Africa and Peru. 

He served as Project Manager for the Trottier Energy Futures Project (TEFP), and most recently, for the Environmental Commissioner of Ontario, for defining minimum cost "pathways" and strategies for reducing greenhouse gas (GHG) emissions for Canada, and for Ontario, respectively, to 2050.

He is a Director of the Energy Council of Canada and served as a Member of a World Energy Council Committee on "Global Energy Scenarios to 2060". He has served as Director or Trustee for approximately 25 publically traded companies, private corporations, regulatory agencies, University, and advocacy organizations. 

He completed his undergraduate and postgraduate studies in Civil Engineering at University of Manitoba and at Imperial College, University of London, respectively, followed by post-doctoral studies, in economics, environmental science and systems methodology, at Harvard University.